(1) Field of the Invention
The present invention relates to a liquid applicator, including writing implements such as felt pens and cosmetic applicators such as eyebrow applicators etc., and more detailedly relates to a liquid applicator of a replaceable cartridge type which enables stable ink supply to a pen core thereof.
(2) Description of the Prior Art
Conventionally, as a writing implement that is a typical applicator, a felt pen using a replaceable ink cartridge is disclosed in Japanese Utility Model Application Laid-Open Hei 6 No.45776.
A cartridge replaceable writing implement of this type comprises, as shown in FIG. 1, a barrel body 100 composed of a front barrel 101 and a rear barrel 102 separably screw-fitted to front barrel 101. This front barrel 101 is sectioned by a partition 103 into a front sleeve 104 and a rear sleeve 105.
A cylindrical projection 106 is formed inside rear sleeve 105 of front barrel 101, concentrically on its axis. A replaceable cartridge 400 holding ink W is removably attached so that its front end is fitted to this cylindrical projection 106. That is, the front end is tightly sealed by a sealing ball 402 in cooperation with a sealing ball seat 401 at the front end of cartridge 400 and when the sealing of this sealing ball 402 is released, ink W inside cartridge 400 is introduced to a communication passage 107 of cylindrical projection 106.
Provided at the front end of front sleeve 104 of front barrel 101 is a sealing sleeve 108, through which a collector 200 is inserted into front sleeve 104. This collector 200 is retained loosely or with a gap with respect to an inner peripheral surface 104a of front sleeve 104 so as to allow air communication with the atmosphere. Formed in this collector is an axial communication passage 201 that is in contact with and in communication with communication passage 107 of cylindrical projection 106.
A plastic mouthpiece (holder) 200a is formed on the front side of collector 200 so that a pen core 202 is inserted into and held by the front end portion of communication passage 201. The rear end face, designated at 200b, of collector 200 is abutted on partition 103 inside front barrel 101. A trunk core 203 is provided with its front end 203a inserted into communication passage 201 and joined to pen core 202 while its rear end 203b is extended to and loosely fitted to communication passage 107 of cylindrical projection 106 formed on the rear sleeve 105 side of front barrel 101 with a gap A created with respect to the inner periphery of communication passage 107. With this arrangement, ink W stored in cartridge 400 is introduced to the communication passage 201 side of collector 200 via communication passage 107 of cylindrical projection 106 and permeates trunk core 203 to be supplied to the pen core 202 side.
Formed further on the outer peripheral portion of collector 200 is an ink collecting portion 300, which is composed of a multiple number of collector vanes 301 arranged comb-like in the axial direction with intervals of a desired spacing D. An ink slit 302 allowed to communicate with the atmosphere is formed extending in the axial direction across all collector vanes 301. The open end, designated at 302a of this ink slit 302, on the collector rear end face 200b side, is adapted to communicate with communication passage 107 of cylindrical projection 106 through a gap B.
That is, this gap B establishes communication between ink slit 302 formed in the outer peripheral portion of collector 200 and communication passage 107 of cylindrical projection 106, so that variation in pressure inside cartridge 400 due to temperature rise from, for example, body temperature of the hand holding barrel body 100 during writing, is relieved by temporarily retaining excessive ink W overflowing from such internal pressure variation, thus preventing ink W from overflowing from the front end side of front sleeve 104.
Conventional writing implements with no replaceable ink storage portion (cartridge) are classified into two types as an ink conduit from the ink storage portion: a configuration in which the collector's center slit is extended radially inward so as to reach the trunk core inside the bore (which will be called the first type: Japanese Patent Application Laid-Open Hei 2 No.81666, for example); and another configuration in which the center slit, instead of being in contact with the trunk core, is extended to the collector's rear end and is brought thereat in direct contact with ink (which will be called the second type).
In the first type, despite the fact that the trunk core is in direct contact with the center slit, since the trunk core, presenting stronger capillary attraction than the center slit, is brought in contact with the gap of the center slit, the ink is unlikely to move smoothly to the center slit in response to the pressure rise due to a temperature rise inside the ink storage portion, revealing inefficiency of the temporal ink storing function of the collector.
For the writing implements with no replaceable ink storage portion, the full range of collector's performance can be obtained by providing the center slit of the second type. In contrast, in a writing implement with a replaceable ink storage portion (replaceable cartridge), the diameter of the cylindrical portion to which the cartridge is fitted is limited (because the diameter of the mouth is limited so that the diameter of the writing implement will not become too large), so that it has been impossible to directly join the cartridge to the ink slit opening at the collector's rear end.
However, for the applicators, i.e., felt pens having the above configuration, open end 302a of ink slit 302, opening on the rear end face 200b of collector 200 is put in communication with communication passage 107 of cylindrical projection 106, an abutment face 103a of partition 103 inside front barrel 101, or the abutment face that rear end face 200b of collector 200 abuts, is formed with a stepped, concave portion 109, so as to create a gap B between abutment face 103a of partition 103 and rear end face 200b of collector 200, correspondingly to open end 302a of ink slit 302, for establishment of communication. However, when front barrel 101 is resin molded using a die elongation and/or sink due to contraction of partition 103 that sections front sleeve 104 and rear sleeve 105 tend to occur, so that the dimensions of gap B on the rear end face 200b side of collector 200 tend to vary.
Gap B formed on the rear end face 200b side of collector 200 should be formed with a predetermined dimensional accuracy so that ink W introduced from cartridge 400 by way of communication passage 107 of cylindrical projection 106 to ink slit 302 of ink collecting portion 300 will be smoothly introduced and flow by the capillary attraction to ink slit 302. Therefore, if the size of gap B varies as stated above, it is impossible to provide a stable, smooth ink channel to ink slit 302. Particularly in the case where the ink channel is narrowed and blocked, it becomes difficult to supply ink to collector 200 so ink directly passes through trunk core 203 being excessively supplied to pen core 202, which in turn spews ink when the pressure inside cartridge 400 rises due to a temperature rise.
Further, since rear end 203b of trunk core 203 being inserted to the rear sleeve 105 of front barrel 101 should be loosely placed with gap A with respect to the wall surface of communication passage 107 of cylindrical projection 106, when the dimensions of trunk core 203 unbearably deviate from the predetermined, design values, or when trunk core 203 is deformed during assembly by some external force and assembled as is, gap A between the wall surface of communication passage 107 of cylindrical projection 106 and the outer periphery of trunk core 203 varies with respect to the circumferential direction, making it difficult to provide stable ink supply to ink slit 302.
In a writing implement of the type where the ink slit of the collector is in direct contact with the ink flowing out from the ink storage portion (cartridge), the dimensions of the ink slit are of importance for balancing the replacement of ink with air. As in the above writing implement where the cylindrical projection (106) of the front barrel is fitted to the cartridge and gap A that is in direct communication with ink is formed between the trunk core and the inner peripheral surface of the cylindrical projection, the writing performance will be determined depending upon the relationship between gap A and the physical properties, especially the viscosity of the ink.
The above gap A functions as the site for replacement of the ink from the cartridge (ink storage portion) with air inside the collector and the easiness of replacement is determined by the size of the gap.
During usual writing, ink transfers from the pen core to a medium to be written in such as paper etc., while ink from the cartridge is supplied to the pen core by way of the trunk core. The ink in the cartridge is drawn to move by the capillary attraction to the trunk core, which causes reduction in pressure inside the cartridge. This reduction in pressure is cancelled by replacing ink with air entering gap A together with ink, or the entrance of the air into the cartridge while the designed, normal amount of ink flow during writing is maintained.
However, when gap A is narrow, it becomes difficult to replace ink with air in gap A, so that the replacement will not occur unless the reduction in pressure inside the cartridge becomes extremely large. When the reduction in pressure inside the cartridge cannot be cancelled, the degree of reduction of pressure grows, inhibiting the ink inside the cartridge from being drawn out by the capillary attraction to the trunk core and hence causing tenuous line drawing and writing failures such as ink starvation. When a high-viscous ink is used, the speed of replacement of ink with air during writing becomes retarded, also causing ink starvation.
Gap A, in addition to providing the function of air replacement, creates an interface between ink and air when the pen core is directed downward, to prevent ink from dropping from the pen core during writing by the surface tension arising at that interface, thus preventing increase in ink flow amount during writing and ink leakage (forward leakage) from the pen core and stabilizing ink flow.
Since ink can be easily replaced when gap A is large, no writing defects such as ink starvation during writing will occur. However, for example, when it is evaluated whether ink leaks forwards from the pen core under the conditions wherein the pen is placed at 50.degree. C. for 7 days with its pen tip capped and oriented downward, the surface tension of the ink decreases with temperature increase, hence the capability of gap A for retaining ink weakens, leading to ink leakage from the pen core or the forward leakage.